Magnetic shuffling of coronal downdrafts

Abstract

Context. Channelled fragmented downflows are ubiquitous in magnetized atmospheres, and have recently been addressed based on an observation after a solar eruption. <BR /> Aims: We study the possible back-effect of the magnetic field on the propagation of confined flows. <BR /> Methods: We compared two 3D magnetohydrodynamic simulations of dense supersonic plasma blobs that fall down along a coronal magnetic flux tube. In one, the blobs move strictly along the field lines; in the other, the initial velocity of the blobs is not perfectly aligned with the magnetic field and the field is weaker. <BR /> Results: The aligned blobs remain compact while flowing along the tube, with the generated shocks. The misaligned blobs are disrupted and merge through the chaotic shuffling of the field lines. They are structured into thinner filaments. Alfvén wave fronts are generated together with shocks ahead of the dense moving front. <BR /> Conclusions: Downflowing plasma fragments can be chaotically and efficiently mixed if their motion is misaligned with field lines, with broad implications for disk accretion in protostars, coronal eruptions, and rain, for example. <P />Movies associated to Figs. 2 and 3 are available at <A href="http://www.aanda.org">http://www.aanda.org